Android Crashing when using a FragmentPagerAdapter

Okay, I hope someone may be able to help. I have spent tonight trying figure this out, I just seem to understand it.

I have created a translation app using 4 Fragments & FragmentPagerAdapter, however it runs fine on the surface up to when I click on the 4th column and then the app crashes and closes.

Logcat is cut down... the top section shows first sign why it crashes, section shows fatal exception and dies. When scrolling across it shows different names than it states on the tab E.g - see below for log cat

java.lang.NullPointerException: Attempt to invoke virtual method 'void android.media.MediaPlayer.pause()' on a null object reference
at ...ColorsFragment$1.onAudioFocusChange(ColorsFragment.java:26)
at ...AudioManager$FocusEventHandlerDelegate$1.handleMessage(AudioManager.java:2147) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:148)
at android.app.ActivityThread.main(ActivityThread.java:5417)
at java.lang.reflect.Method.invoke(Native Method)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)